Blow molding is a well-known method for producing a variety of plastic products, particularly receptacles or hollow vessels including fuel tanks, containers, and the like. In general, a typical process of blow molding a multiple layer fuel tank involves extruding a multilayer tubular parison into an open mold and around spreader pins and a blow pin. The spreader pins expand to stretch the hot parison in a radial direction toward mold halves. The mold halves close together around the stretched parison and the blow pin injects pressurized gas into the interior of the parison to displace the parison into conformity with interior surfaces of the mold halves. Also, a carrier and various fuel system components, such as fuel level sensors, venting devices, fuel pumps, fuel filters, and the like may be carried by the blow pin and molded in place. But placement of the components in the tank during blow molding can be difficult, because the components attach to the inside surface of the molded fuel tank only after the mold has been closed and the parison shaped against the mold halves.
Also, fuel tanks are often produced by blow molding an extruded multiple layer parison that may include multiple structural, barrier, and adhesive layers. But extrusion typically requires dedicated extrusion equipment that produces fixed quantities of parison layers of fixed size and fixed configuration. Accordingly, there is limited flexibility in producing fuel tanks of variable quantity, size, and configuration of layers.